Process of treatment of textile material with silica



United States atent flice PROCESS OF TREATMENT OF TEXTILE MATERIAL WITH SILICA Ralph F. Nickerson, Marhlehead, Mass., assignor to Mon-- santo Chemical Company, St. Louis, Mo., a corporation of Delaware No Drawing. Application March 30, 1950, Serial No.- 152,985

7 Claims. (Cl. 117-1388);

The present; invention relates to processes for treating textile materials prepared from synthetic, fiber-forming polymers which contain imido groups, particularly for the purpose of increasing the inter-fiber friction of such materials, and, in the case of textile fabrics, of increasing their resistance to slippage, snagging and running.

It isone object of this invention to provide improved processes for treating textile materials prepared from synthetic fiber-forming polymers which contain imido groups to increase the inter-fiber friction of such materials and at the same time retain the desirable characteristics of the materials such as hand, feel and. the like.

A further object of this invention is to. provide improved processes for treating textile fabrics, and particularly knitted textile fabrics, comprising synthetic fibers prepared from fiber-forming synthetic linear polyamides to increase their run, snag and slip resistance and at the same time. retain the natural hand. and feel. of the fabric.

A further object of this invention is to provide. improved processes for treating textile fabrics, and particularly knitted textile fabric, comprising synthetic fibers prepared from fiber-forming synthetic linear polyamides to provide the fabric with a finish which is resistant to washing and dusting and which imparts body, firmness and snag, run and slip resistance to the fabric without de.-. tracting appreciably from the desirable characteristics of the fabric.

Still further objects and advantages of this invention will appear in thefollowing description and the appended claims.

The term textile materialas. used herein. is intended to cover textile fabrics, both woven and knitted, which are prepared from textile fibers, and textile fibers.

T are intended to include yarns, continuous and non-continuousfilaments and staple fibers.

The present invention'is carried out, in general, by wetting out a textile material prepared from synthetic fiber-forming polymers which contain imido groups, for example, nylon textile materials prepared from polyhexamethylene-adipamide linear polymers, in. a dilute acidic aqueous solution of colloidal. silica at least until the desired amount of silica has been deposited on the textile material, after which the material is removed from the solution and dried, or in some cases, if preferred, is dried, rinsed and dried a. second time.

water-soluble salts of which the water-soluble ammonium salts. of inorganic or organic acids are preferred. By

wet-ting out is meant an operation in which the textile material is completely submerged in the Solution at all times, or an operation in which the textile material is alternately immersed in the solution and removed therefrom, oran operation in which the textile material and the solution are tumbled in a suitable apparatus so that the material is not entirely immersed in the solution at all, times. Agitation of the solution and/or the textile material is preferred in order to bring all of. the material in contact with the solution.

It has presently been found that under. the conditions of operation set forth immediately above, and described in greater detail hereinafter, the particles of colloidal silica in the solution migrate from the solution to the textile material. If the treatment is carried out. for a sufficient period of time substantially all of the colloidal e terms fibers. or textile. fibers? as used herein 4 Thistreatment is preferably carried out, in the presence of silica migrates from the solution to the textile material, leaving a solution which is substantially free of colloidal silica. The rate of migration of the colloidal silica from the solution to. the textile material is primarily dependent, on the pH of the solution, the amount of water-soluble salts present in the solution, if such salts are used, and the temperature of the solution. By lowering the pH of the. solution, increasing thev concentration of the salt in the solution and/or increasing the temperature of the solution, the rate of migration of the colloidal silica from the solution to the. textile material is increased.

The processes of this invention should be distinguished from those processes in which a textile material of the type herein described. is immersed in a solution containing solid substances where the. amount of solid substances deposited on the material is equal to the amount of liquid picked up by the material multiplied by the concentration of solid substances in the solution, or from those processes in which a textile material is immersed in a solution containing solid substances wherein the solid substances are precipitated on the material. It is believed that in carrying out the processes of the present invention the colloidal silica migrates from the solution to the textile material because of a difference in electrostatic charge between the material and the colloidal. silica, but irrespective of this explanation it has presently been observed that the colloidal silica is. deposited on the textile material by migration from the solution rather than by any substantial amount of precipitation from the. solution.

In carrying outthe processes of this invention it is possible to proceed in one of two. ways, either of which gives satisfactory results. The. first mode of procedure comprises wetting out the textile material. in. a dilute acidic aqueous solution of colloidal silica, using. an amount of liquid considerably in excess of the weight of the material, which solution contains an amount of colloidal silica in. excess of that which it is desired to apply on the textile material, and then continuing. the treatment until the desired amount of silica has. migrated from the solution to, the material. In the foregoing procedure the amount of silica applied to the. textile material is readily determined by testing. small aliquot portions of the solution as the treatment'proceeds to ascertain the amount of silica present therein and calculating, therefrom the amount of silica applied to the material. The second mode of procedure comprises wetting out the textile material in a. dilute acidic aqueous solution of colloidal silica using an amount of liquid considerably in excess of the weight of the material, which solution contains an amount of colloidal silica substantially equal to the amount of silica. which it is desired to apply to the textile material, and then continuing the treatment until substantially all of the, colloidal silica has migrated from the solution to the material. of the treatment is readily determined by the fact that the initially turbid solution becomes clear when the treatment is finished.

The amount of silica applied to the textile materials in either ofv the above procedures should be sufiicient to increase the inter-fiber friction of the textile material, and, in the case of fabrics, to increase their snag, run and slip resistance, but preferably, insufiicient to produce. a. stiffened. material or a material which has a harsh hand. Satisfactory results have been obtained by allowing from 0.5 to 4% by weight of colloidal silica based onthe texthe material to migrate from the solution to the material.

In carrying out either of the procedures hereinbefore described, it is preferable to use the treating solutions in amounts considerably in excess of the. weight of the textile material being treated, that is, in amounts of from about 61 to 20. times the Weight of the material. Thus, the. weight ratio of the solution to material is preferably between about 6:1 and 20:1. It is possible, however, in some instances to vary these ratios. For example, it is possible to use a weight ratio of solution to textile material. of 5:1 in those instances where woven textile fabrics are being treated. It is also possible to use higher. weight ratios of solution. to textile. material, for example, a weight ratio of 50:1. However, in such a case it is gen- In this procedure the duration erally necessary to use larger pieces of equipment, and

more water is consumed than is actually required in most instances.

It is possible in carrying out the procedures described herein to vary the colloidal silica concentration of the solution to a certain extent depending on the amount of silica which is to be applied to the textile material and the weight ratio of solution to textile material used. It is preferred to use a solution containing from 0.5 to 8% by weight of colloidal silica based on the dry weight of the textile material. When the weight ratio of solution to textile material is between 6:1 and 20:1, the solution should contain from 0.025% to 0.4% by weight of colloidal silica for best results.

The temperature of the acidic aqueous solutions of colloidal silica during the textile treating period may be varied to a considerable extent depending primarily on the acidity of the solution and whether water-soluble salts are employed therein. In general, the rate of migration of the colloidal silica from the solution to the textile material is increased by raising the temperature of the solution. Solution temperatures of 80 to 160 F. have been used successfully. However, iit is possible to use temperatures below 80 F. although temperatures between 60 and 80 F. are not normally satisfactory unless watersoluble salts are employed. Temperatures above 160 F. give a more rapid rate of migration but are not too satisfactory in some instances because an uneven distribution or deposition of the silica on the material may result, and this is particularly true when Water-soluble salts are used.

In carrying out the procedures of this invention, satisfactory results have been obtained by treating the textile material in an acidic aqueous solution of colloidal silica adjusted to a pH between about 3 and 6.5. The acidity of the solution has a considerable effect on the rate of migration of the colloidal silica to the textile material, and by lowering the pH or increasing the acidity of the solution it is possible to obtain a more rapid migration of the silica particles. It is sometimes possible to increase the acidity of the solution so that the pH thereof is below 3, but this is not generally advisable because fibers or filaments prepared from fiber-forming polymers containing imido groups often hydrolyze under highly acid conditions, for example, at a pH below about 2. On the other hand, the process will generally not operate successfully unless the pH of the solution is slightly below 7. It is preferred to use solutions which have a pH between about 4 and 5 since such acidity is not harmful to the textile materials and promotes relatively rapid migration of the colloidal silica from the solution to the material.

The acidic aqueous colloidal solutions of silica employed herein may be prepared in various ways as will be apparent to those skilled in the art. However, such colloidal solutions should be stable for at least one hour under the conditions of operation. The term aqueous solution of colloidal silica as employed herein is intended to exclude dispersions prepared by mechanically dispersing finely ground silica gels. A preferred way of preparing an acidic aqueous solution of colloidal silica for use in accordance with this invention is to admix a stable, alkaline reacting silica aquasol with an amount of water-soluble acid reacting substance sufficient to form a solution having the desired acidity.

A stable alkaline reacting silica aquasol which is suitable for the above purpose may be prepared in a variety of ways. One suitable method consists in treating an alkali silicate with a cation exchange material, as described in the patent to Paul C. Bird, No. 2,244,325. A preferred method for the preparation of a suitable stable alkaline reacting aquasol consists in reacting a mineral acid such as sulfuric acid with a water-soluble silicate such as sodium silicate until an acid reacting sol is obtained. This sol soon sets up into a gel which is broken up into lumps and washed with water to remove the electrolytes formed during the reaction between the acid and the silicate. The washed gel is covered with a weak aqueous solution of a substance capable of forming hydroxyl ions, for example, sodium hydroxide. After the gel has absorbed the hydroxyl ions, it is separated from the excess solution and is heated, while avoiding the evaporation of water, for example, in an autoclave, until the major portion of the gel is converted to a sol. The sol is then separated from the unconverted gel as, for example, by centrifuging. The foregoing process is described in greater detail in the patent to John F. White, No. 2,375,738.

As examples of Water-soluble acid reacting substances which are admixed with the above described alkaline reacting sols to produce the acidic aqueous solutions of colloidal silica may be mentioned water-soluble acid reacting salts such as sodium bisulfate, sodium dihydrogen phosphate and the like; water-soluble organic acids such as acetic acid, formic acid, tartaric acid and the like and water-soluble inorganic acids such as hydrochloric acid, sulfuric acid and the like. It is preferred to use volatile acids and particularly volatile organic acids such as acetic acid, or formic acid and the like. If non-volatile acid reacting substances are employed, it is preferable to rinse the fabric which has been treated with the colloidal silica solution after the fabric has been dried.

As pointed out previously herein it is preferred to use water-soluble salts in the solution of colloidal silica in carrying out the processes of this invention. The reason for this is that water-soluble salts are helpful in speeding up the rate of migration of the colloidal silica particles from the solution to the textile material, the rate of migration increasing as the concentration of the salt in the solution of colloidal silica is increased. When water-soluble salts are employed it is preferred to use acidic aqueous solutions of colloidal silica which contain from 0.3 to 7% by weight of such water-soluble salts. As examples of water-soluble salts which are useful in the processes of this invention may be mentioned the water-soluble neutral alkali metal inorganic salts such as NaCl, KCl, Na2SO4, K2504 and the like; and water-soluble ammonium inorganic salts such as ammonium chloride, ammonium sulfate and the like. The water-soluble ammonium salts are preferred, and especially those ammonium salts which contain at least a divalent cation as, for example, ammonium sulfate.

The duration of the treatment of the textile materials with the acidic aqueous solutions of colloidal silica as described herein depends to a considerable extent on the acidity of the solution, the temperature of the solution and the use of water-soluble salts therein. In general, when salts are employed the treating period required varies between about 5 and 30 minutes. In the absence of such salts longer treating periods are generally required and in some instances, particularly at pH values close to 7 and at low temperatures, minutes may be necessary to complete the treatment. The duration of the treatment, therefore, is generally within the range of 5 to 120 minutes.

It has presently been found that it is possible to improve the permanency of the finish which is produced on the textile materials in accordance with the processes hereinbefore described, by treating the textile material with an aqueous dispersion of negatively charged synthetic resin particles. The textile material may be treated with such a dispersion, after the treatment with the colloidal silica, under the same conditions of acidity and temperature and in the presence of salts as were used in the colloidal silica treatment. However, it is preferred to carry out the treatment of the textile materials with an acidic aqueous solution of colloidal silica in which the aqueous dispersions of the negatively charged synthetic resin particles have been incorporated so that the entire treatment is carried out in one operation using the procedures hereinbefore described. In either of these modes of procedure the negatively charged synthetic resin particles migrate from the water phase to the textile material and provide, together with the silica, a slip resistant finish which is resistant to washing and dusting. In the case of textile fabrics a snag, run and slip resistant finish which is resistant to washing and dusting is provided by such processes. Moreover, the materials also have improved body and firmness.

The aqueous dispersions of negatively charged synthetic resin particles may be either dispersions of thermosetting or thermoplastic resins. Preferred dispersions are the aqueous dispersions of negatively charged, hydrophobic thermoplastic resins as, for example, aqueous dispersions of plasticized or unplasticized polystyrene, plasticized polyvinyl acetate, plasticized polyvinyl butyral and the like. The quantity of such resins used may be Varied to some extent, but the resins preferably should be used in amounts sutficient to increase the Wash resistance preciable stiffening of the textile material. In general,

hum about 05 to 4% By weight of the; resin based (in the fabric gives satisfactory results. When theweight ratio of the treating solution to the textile material is between about 6:1 and 20:1, it is preferred to use solutions which contain from 0.025 to 0.4% by weight of the resin.

A further understanding of the present invention will be obtained from the following examples which are in= tended to further illustrate this invention but not to limit the scope thereof, parts and percentages being by weight unless otherwise specified.

Example I A stable alkaline reacting silica aquasol was first prepared using the procedure described in Example 1. of the patent to John F. White, No. 2,375,738. The resulting so], which contained about 12.5% SiO-2 and had a pH of about 9.2, was concentrated by evaporating water therefromuntil it contained 15% SiOz.

One partgof desized and dyed pre-boarded nylon hosiery, the filaments of which were prepared from polyhexamethylene-adipamide linear polymer, was alternately immersed in and removed from 8 parts of an aqueous solution containing 20% of the silica aquasol described above: (15% silica) and 5% ammonium sulfate and adjusted to a pH of 5 with acetic acid. The above percentages of the silica aquasol and the ammonium sulfate were calculated on the dry weight of the hosiery. The temperature of the solution was 90 F. After being alternately immersed in and removed from the solution for a period of 30 minutes, the hosiery was removed from the solution and placed on form boards and dried. The solution was clear and was found to be substantially free of colloidal silica. During the treatment the colloidal silica migrated from the solution to the hosiery. The hosiery thus treated was scratched with weighted sand paper and developed but a few snags under these conditions whereas untreated hosiery tested in the same manner developed a large number of snags and holes.

Example [I One part of desized and dyed pre-boarded nylon hosiery, the filaments of which were prepared from polyhexamethylene-adipamide linear polymer, was alternately immersed in and removed from 8 parts of an aqueous solution containing 20% of the silica aquasol (15% silica), prepared as described in the first paragraph of Example I, 5% ammonium sulfate and 6% of an aqueous dispersion of 40% solids content of which 60% consisted of polystyrene and 40% consisted of dibutyl phthalate as a plasticizer, the percentages of the aquasol, ammonium sulfate and aqueous dispersion being calculated on the dry weight of the hosiery. The pH of the aqueous solution was adjusted to S with acetic acid, and the temperature of the solution was 90 F. After the hosiery was treated for 15 minutes, as described above, the temperature of the solution was raised to 120 F. and the treatment was carried out for an adidtional 15 minutes. The treating solution was clear and substantially free of colloidal silica and plasticized polystyrene, both of which had migrated from the solution to the hosiery. The hosiery was removed from the solution placed on forms and then dried. The hosiery was observed to have improved body and firmness and also exhibited excellent snag-resistance when scratched with weighted sandpaper. After 5 hand launderings the body, firmness and snagresistance of the treated hosiery were only slightly reduced. This shows that the colloidal silica-polystyrene finish on the hosiery is highly resistant to laundering.

Example III One part of desized and dyed pre-boarded nylon hosiery, the filaments of which were prepared from polyhexamethylene-adipamide linear polymer, was agitated in 8 parts of an aqueous solution containing 5% of the silica aquasol (15% silica), prepared as described in the first paragraph of Example I, and 50% of ammonium chloride, both percentages being calculated on the dry weight of the hosiery. The pH of the solution was adjusted to 4 with acetic acid, and the temperature of solution was 120 F. The hosiery was agitated in the above solution for 30 minutes during which time the colloidal silica migrated from the solution to the hosiery and the solution became clear and substantially free of colloidal silica. The hosiery was then removed from the solution 6 and dried. The treated hosiery Was scratched with weighted sandpaper and was almost completely resistant tosnagging whereas untreated hosiery was badly damaged under the same conditions.

Example IV One part of loose nylon staple fibers, prepared from polyhexamethylene-adipamide linear polymer, was agitated in 10' parts of an aqueous solution containing 20% of the silica aquasol (15% silica), prepared as described in the first paragraph of Example I, and 5% ammonium sulfate, both percentages being based on the dry weight of the. fibers. The pH of solution was adjusted to 5 with acetic acid, and the temperature of the solution was F. The staple fibers were agitated in the solution for 15 minutes and then removed from the solution and dried. It was observed that the inter-fiber friction of the staple fibers was considerably increased by the treatment and they were thereby rendered more amenable to spinning.

In the foregoing examples the treatment of knitted nylon hosiery and staple fibers, the fibers of which were prepared from polyhexamcthylene-adipamide linear polymer, is illustrated. However, it is possible to treat nylon woven fabrics in the same manner to improve their resistance to slippage. Moreover, other synthetic fibers which contain imido groups, for example, fibers prepared from polyhexamethylene-sebacamide linear polymers, or fabrics prepared from such fibers are also successfully treated in accordance with the processes described herein. Generally, it is possible to treat in accordance with the processes of this invention textile materials prepared from synthetic fiber-forming linear polymers which contain imido groups, for example, synthetic linear polyamides prepared in accordance with U. S. patents, No. 2,071,250; 2,130,523 and 2,130,948. The processes of this invention are preferably utilized in the treatment of knit fabrics such as nylon hosiery prepared from filaments of polyhexamethylene-adipamide linear polymers.

This invention is not intended to be limited to the particular stage of processing of textile materials as il lustrated in Examples I to 111 since it is possible to treat the textile materials before they are dyed, or at the same time they are being dyed, or immediately after they are dyed. However, it is preferred to treat the textile materials during the dyeing operation or after they are dyed, ainddpreferably in the same apparatus in which they are Various modifications and changes may be made in the processes described herein as will be apparent to those skilled in the art to which this invention appertains without departing from the spirit and intent of this invention. It is accordngly intended that this invention shall not be limited except by the scope of the appended claims.

What is claimed is:

l. A process of treating knit hosiery comprising filaments prepared from fiber-forming polyhexamethyleneadipamide linear polymers which comprises wetting out said hosiery in from 6 to 20 times its own dry weight of a composition consisting of a dilute acidic aqueous solution having a pH between about 3 and 6.5 and containmg (1) from 0.025% to 0.4% by weight of colloidal silica and (2) from 0.3 to 7% by weight of a water-soluble salt selected from the group consisting of ammonium and alkali metal salts of hydrochloric and sulfuric acids, until substantially all of the colloidal silica originally present in said composition migrates from said composition and deposits on said hosiery, whereby said composition is substantially free of colloidal silica, and then drying said hosiery.

2. The process according to claim 1, but further char- ?cterized in that the water-soluble salt is ammonium sulate.

3. The process according to claim 1, but further characterized in that the water-soluble salt is ammonium chloride.

4. The process according to claim 1, but further characterized in that the acidic solution is prepared by admixing a stable, alkaline-reacting silica aquasol with acetic acid and said water-soluble salt.

5. The process according to claim 1, but further characterized in that the acidic solution is prepared by admixing a stable, alkaline-reacting silica aquasol, formic acid and said water-soluble salt.

6. A process of treating dyed hosiery consisting of filaments prepared from fiber-forming polyhexamethyleneadipamide linear polymers, which process is carried out in a dyeing apparatus, which comprises wetting out said hosiery in said dyeing apparatus, in which said hosiery has also been dyed, in from 6 to 20 times its own dry weight of a composition consisting of an acidic aqueous solution having a pH between about 3 and 6.5 and containing (1) from 0.025 to 0.4% by weight of colloidal silica and (2) from 0.3 to 7% by weight of a water-soluble salt selected from the group consisting of ammonium and alkali metal salts of hydrochloric and sulfuric acids, maintaining said hosiery in contact wtih said composition in the dyeing apparatus until substantially all of the colloidal silica migrates from the composition to the hosiery and deposits thereon, and until said composition is substantially free of colloidal silica, and thereafter drying said hosiery.

7. A process of treating textile materials of staple fibers or knit fabrics prepared from fiber-forming filaments which contain amido groups which comprises wetting out said materials in from 5 to 50 times their own weight of a composition consisting of an acidic aqueous solution having a pH between about 3 and 6.5 and containing (1) from 0.5 to 4% by weight of colloidal silica based on the dry weight of the materials and (2) a water-soluble salt selected from the group consisting of ammonium and alkali metal salts of hydrochloric and sulfuric acids, said salt being present in an amount sufficient to aid exhaustion of the colloidal silica onto said textile materials, maintaining said textile materials in contact with said composition until substantially all of the colloidal silica migrates from the composition to said materials, whereby said composition is rendered substantially free of colloidal silica, and then drying the textile materials.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Mellors Modern Inorganic Chemistry, revised edition, 1939, pages 246, 247, 248. 

7. A PROCESS FOR TREATING TEXTILE MATERIALS OF STAPLE FIBERS OR KNIT FABRICS PREPARED FROM FIBER-FORMING FILAMENTS WHICH CONTAIN AMIDO GROUPS WHICH COMPRISES WETTING OUT SAID MATERIALS IN FROM 5 TO 50 TIMES THEIR OWN WEIGHT OF A COMPOSITION CONSISTING OF AN ACIDIC AQUEOUS SOLUTION HAVING A PH BETWEEN ABOUT 3 TO 6.5 AND CONTAINING (1) FROM 0.5 TO 4% BY WEIGHT OF COLLOIDAL SILICA BASED ON THE DRY WEIGHT OF THE MATERIALS AND (2) A WATER-SOLUBLE SALT SELECTED FROM THE GROUP CONSISTING OF AMMONIUM AND ALKALI METAL SALTS OF HYDROCHLORIC AND SULFURIC ACIDS, SAID SALTS BEING PRESENT IN AN AMOUNT SUFFICIENT TO AID EXHAUSTION OF THE COLLOIDAL SILICA ONTO SAID TEXTILE MATERIALS, MAINTAINING SAID TEXTILE MATERIALS IN CONTACT WITH SAID COMPOSITION UNTIL SUBSTANTIALLY ALL OF THE COLLOIDAL SILICA MIGRATES FROM THE COMPOSITION TO SAID MATERIALS, WHEREBY SAID COMPOSITION IS RENDERED SUBSTANTIALLY FREE OF COLLOIDAL SILICA, AND THEN DRYING THE TEXTILE MATERIALS. 